Solid ink shrinks by about 17% by volume when it freezes. If the flexible, drop ejecting membranes in a MEMSJet printhead are in intimate contact with the ink as it freezes they can be deformed to the point of breaking due to this shrinkage.
Note, the term “MEMS” refers to “Micro Electromechanical System”. Hence, the term “MEMSJet printhead” generally refers to a Micro Electromechanical System ink drop ejector marking devices. A general discussion of such devices may be found in U.S. Pat. No. 6,357,865, “Micro-electro-mechanical fluid ejector and method of operating same”, issued 19 Mar. 2002 to Joel A. Kubby et al., especially the text appearing from col. 1, line 5 to col. 2, line 32.
Likewise, damage can be incurred during the thawing phase due to a buildup of pressure. Once broken, the membrane can no longer be used to eject drops and worse, ink gets under the membrane and into the rest of the vent system ruining the printhead. The thawing process can also cause enough pressure buildup to delaminate the nozzle plate from the actuator walls thereby destroying the head. The combination of solid ink and membrane based MEMS direct marking devices is new and the problem has not been encountered before.
Thus, there is a need for the present invention.